This program continues to focus on elucidating the discrete regional susceptibility to atherogenesis. In particular, the complex interplay of mechanical forces and chemical mediators which impinge on platelet vascular interactions and on cells of the vessel wall and their interaction with the extracellular matrix will be elucidated. Distinct and overlapping signaling pathways will be integrated by genomic and proteomic interrogation of determinants of the balance between susceptibility to and protection from atherosclerosis. Particular attention will be paid to how traditional risk factors, including age, hyperlipidemia and gender condition cell signaling pathways of relevance to inflammation and oxidant stress. In Project 1 the role of the eicosanoid pathway downstream of the cyclooxygenase enzymes will be examined. Genetic and pharmacological approaches will be combined to elucidate the distinct roles of prostaglandins in the development and regression of atherosclerosis, blood pressure control and the response to thrombosis. Metabolomic analyses and novel quantitative indices of oxidative stress will be utilized to integrate the impact on atherosclerosis in vivo with the response to inflammatory and oxidant stimuli VSMC in vitro, as phenotypic outcomes in vivo are related to genomic and proteomic consequences of receptor deletion in vitro. In Dr. Bennet's project a careful analysis will be performed of the role that transmembrane and cytoplasmic domains play in the regulation of the integrin Alpha-v Beta-3. Particular emphasis will be placed on elucidating the structural constraints that govern formation of homomeric and hetromeric interactions between domains of this integrin, which is of relevance to adhesive interactions between vascular cells. These concepts will also be extended to the platelet collagen receptor, the integrin Alpha-2 Beta-1 where structural information will inform the design of specific small molecule antagonists, tested in the models utilized in Project 1. In Dr. Rader's project, we shall investigate the domains of ApoE that are relevant to upregulation of COX-2 in VSMC and the receptors and signaling pathways relevant to this response. A common approach with Project 1 will be adopted in the genomic and proteomic analysis of the response to ApoE. In Project 4 we shall elucidate the mechanism by which CD44, which we have shown to be of relevance in atherogenesis, impacts on integrin dependent cell spreading and actin polymerization. Particular emphasis will be placed on elucidating how CD44 and its ligand, hyaluronic acid, modulate the cell cycle. Finally, we will utilize mice expressing eGFP fluorescent tagged cyclin A to investigate the role of CD44 deletion on cell proliferation during atherogenesis and in the response to injury in vivo. Finally, in Project 5 we shall examine the effect of gender and hyperlipidemia on the discrete expression of genomic subsets in regions of the pig aorta susceptible to and protected from atherogenesis. These studies will be complemented by studies of laminar and disordered laminar shear in vitro: RNA silencing and receptor deletion will be used to elucidate the functional importance of these observations. This program will take an integrated approach to the study of humoral and mechanical signaling in vascular cells. Factors which underlie the cell to cell heterogeneity of this interaction are likely to contribute to the focal nature of atherogenesis.